Self-cleaning tip for airless spray guns



Dec. 3, 1968 T. B. LEGEZA ETAL 3,414,196

SELF-CLEANING TIP FOR AIRLESS SPRAY GUNS Filed Jan. 9, 1967 fIE-IL- INS/ENTERS: 7110mm .5. LEEEZA BY H/ILLIAM l7. AUTHJBH United States Patent SELF-CLEANING TIP FOR AIRLESS SPRAY GUNS Thomas B. Legeza, Toledo, and William D. Gauthier,

Sylvania Township, Lucas County, Ohio, assignors to The De Vilbiss Company, Toledo, Ohio, a corporation of Ohio Filed Jan. 9, 1967, Ser. No. 607,992 Claims. (Cl. 239-106) ABSTRACT OF THE DISCLOSURE This invention comprises a nozzle assembly for a high pressure airless-type spray gun in which the very small discharge orifice is subject to clogging, thereby radically altering the spray pattern and fluid discharge rate of the gun. A slider is provided which may be removed in a direction transverse to the axis of the spray gun, reversed and replaced so that the clogged orifice may be cleaned by material flow in a reverse direction. The slider may also be adjusted transversely to bring different ones of a plurality of discharge orifices into operative position. A hydraulically actuated seal prevents leakage at the interface between the slider and the guide ways of the assembly in which it moves.

BACKGROUND OF THE INVENTION In airless spray coating systems where operating pressures frequently exceed one thousand pounds per square inch, frequent cleaning of the very small discharge orifice of the gun is necessary and is made difficult due to the requirement for completely sealing the removable orifice within the gun body to prevent leak-age at such high pressures. While self-cleaning or reversible orifice spray devices are known in the art and are disclosed in United States Patents 511,728, 949,089 and 3,116,882, a sealing ring or gasket which will permit rotary movement of the elements therein is necessary and the seal effected thereby has proven to be unreliable at high pressures. It has been found that a removable or interchangeable orifice may be associated with a spray gun body by mounting it on a transverse slide mechanism wherein the high pressure of the coating material is utilized to effectively urge a flat seal against the slide to prevent leakage around the gun discharge orifice. A means for quickly reducing the high pressure effecting the seal enables removal. reversal and reinsertion of the orifice slide for cleaning a clogged or partially clogged orifice by flow of fluid in a reverse direction. Incorporated in the slide may be a plurality of different sized discharge orifices which may be selectively placed in operative position by movement of the slide in a direction transverse to the direction of movement of the coating material or to the axis of the gun.

SUMMARY OF THE INVENTION The invention includes a body assembly adapted to be attached to a conventional airless type spray gun with a movable sealing plunger adapted for slight movement along the axis of the spray gun between a first position away from the transversely guided orifice slide to a second position in contact with the orifice slide. The orifice slide is received by guide ways in the body assembly in either a forward position for normal spraying or reverse position in which a clogged orifice can be cleaned, and can be selectively positioned along the guide ways in either position in order to bring any one of a plurality of orifices carried by the slide into operative position. When a position of the orifice slide has been selected and coating material pressure is applied to the sealing plunger, it moves from its first to its second position at which its outermost end sealingly engages one side of the orifice 3,414,196 Patented Dec. 3, 1968 slide and urges the other side of the orifice slide into engagement with the guide ways.

When the trigger actuated fluid valve of the spray gun is closed, liquid pressure upon the sealing plunger is eliminated and the slide may he removed and reversed for cleaning. If the orifice becomes completely blocked or clogged and prevents the fluid valve from closing completely, the attachment between the holder assembly and the gun body itself may be loosened to increase the volume of the entrapped liquid beyond the fluid valve to decrease the pressure, thus causing immediate closure of the fluid valve, and the consequent reduction in pressure against the slide to permit removal thereof.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view in elevation, partly in cross section, of the reversible tip nozzle assembly of this invention associated with a conventional airless spray gun, showing the removable slide mechanism positioned within its holder assembly, and the relationships between the valve mechanism of the gun body and the sealing plunger within the holder assembly;

FIG. 2 is a cross-sectional view of the orifice slider and holder assembly of this invention, indicating the path of liquid flow past the open valve of the gun assembly and through one of the orifices in the slider; the parts being in reversed position as during a cleaning operation;

FIG. 3 is a front view of the slider and gun, taken along line 3-3 of FIG. 2, and showing the position of the orifices within the slider;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3 but with the orifice slider removed; and

FIG. 5 is a view in elevation of an orifice slider removed from the holder assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the reversible tip assembly is shown associated with a conventional iairless spray gun, generally designated by reference numeral 10. Liquid coating material is supplied through a supply line 11 which connects to an axially extending passage 12 through which a reciprocating valve 13 extends. The reciprocating valve 13 closes upon a valve seat 14 which is formed in the restricted end of a tubular member 15 which forms the terminal portion of the axial fluid passage 12 in the spray gun body 10. The valve 13 is moved away from its seat 14 by a manually actuated trigger 16 and is urged to its normally closed or seated position by a conventional spring or other biasing member (not shown).

Secured to an externally threaded flange 17 on the gun body 10 is the reversible tip structure of this invention. This structure includes a body assembly 18 which, as best seen in FIGS. 2 and 4, has a tapered tubular member 19 and a transversely extending tip holder guide 20 rigidly secured to the outer end of the tubular member 19. An internally threaded nut 22 having a tapered interior passage shaped to match the outer surface of the tubular member 19 is threaded upon the flange 17 of the spray gun 10 to securely hold the body assembly 18 in place.

A seal-ing plunger 23 is coaxially positioned within the tubular member 19. The sealing plunger 23 has a flange 24 which acts with a complementary shoulder 25 on the inner surface of the tubular member 19 to prevent inadvertent removal of the sealing plunger 23. A backup plug 26 is positioned within the tubular member 19 to the rear of the plunger 23, as shown in FIGS. 1, 2, and 4. A retaining ring 27 which is held in an internal groove within the tubular member 19 limits movement of the backup plug 26 to the rear. Between the backup plug 26 and the plunger 23 is an O-ring 28 which is circumjacent a restricted portion of the backup plug 26 to prevent leakage of coating material rearwardly past the backup plug 26.

An axial liquid passage 29 extends through the plunger 23 and a non-axial liquid passage 30 extends through the backup plug 26 to connect the center portion of the rear surface of the plug 26, as shown in FIG. 2, with the space between the plug 26 and the sealing plunger 23, designated by reference numeral 31. The non-axial passage 30 serves to dissipate a portion of the energyinherent in a flowing liquid stream at the very high pressures involved.

Referring to FIGS. 1, 2, 3, and 4, the tip holder guide extends generally transversely of the axial passage 12 to form a slot or guide way having a rear surface 32 adjacent the front sealing portion of the sealing plunger 23 and a forward surface formed by return flanges of two sides of the holder guide 20, designated by reference numerals 33 and 34.

The orifice slide, as seen in elevation in FIG. 5, includes a pair of matching halves, which, when secured together, as by recessed screws 35 and 36, have a rectangular, com plementarily shaped cross section to the ways in the tip holder guide 20. As best seen in FIG. 2, the tip holder slide 37 has one or more internal cavities for positioning a restricted material discharge orifice 38 or 39 therein and has a handle or grip 42 attached to one end. The two slider halves may be separated for removal or inspection of the orifice inserts 38 or 39 by removing the screws 35 and 36.

When the orifice slide 37 is inserted within the tip holder guide 20 in normal spraying position, as shown in FIG. 1, the liquid coating material will flow through an aligned orifice 38 or 39 in a first direction and, when the slide 37 is reversed in the guide 20, as shown in FIG. 2, the liquid coating material will fiow in the opposite direction through an orifice 38 or 39. It will be apparent that the slide 37 may be selectively positioned to align one or the other of the orifices 38 and 39 with the axial passage 29 through the plunger 23 so that the operator may selectively use one or the other of the orifices 38 or 39 in the coating operation, as indicated by the dotted and solid line shown in FIG. 1. A spring biased stop member 43 and spaced apart detents 44 on the slider may be provided to initially position the slider 37 and its orifices 38 and 39.

As previously stated, the high operating pressure of the liquid coating material is utilized to effectively seal the slide 37 with the adjacent end sealing surface of the plunger 23. Referring to FIG. 1, with the slide 37 in position so that an orifice, such as 38, is aligned in operating position with the axial passage 29 in the plunger 23, and with the tapered nut 22 tightly turned upon the threaded flange 17 so that the end of the tubular member 15 is tightly engaged against the adjacent surface of the backup plug 26, liquid under pressure from the passage 30 fills the space 31 between the backup plug 26 and the sealing plunger 23, forcing the sealing plunger 23 forwardly and the backup plug 26 rearwardly. The smaller end of the plunger 23 is urged with high force against the adjacent surface of the slide 37 which is in turn pushed against the forward surfaces 33 and 34 of the tip holder guide 20. Under high operating pressure, an effective seal is formed between the rear surface of the slide 37 and the small end portion of the plunger 23. As long as a high coating pressure is maintained, the slide 37 is rigidly held in its position with its inner surface, adjacent the operating orifice, sealingly engaged with the adjacent surface of the plunger 23. Fluid leakage past the radially outer surface of the plunger 23 and the opposed inner surface of the tubular member 19 can be prevented in any suitable manner as by providing a suitable axially movable seal between the sur faces or by providing a pressure actuated seal including a tapered groove 40, as shown in FIG. 2, which, when under pressure, permits a portion of the plunger 23 to expand and to force the portions external of the groove 40 against the adjacent wall.

When the valve 13 is closed upon its valve seat 14, the force urging the plunger 23 against the interior surface of the slide 37 is released as the pressure drops. The slide 37 is then free to be moved manually to another position or removed for reversal, etc. A common malfunction in an airless coating system of this type is the complete clogging or blocking of the operating discharge orifice 38. If the operating orifice 38 completely closes, the liquid pressure in the space 31 between the plunger 23 and the backup plug 26 which holds the plunger against the slide 37 may not be released, even if the valve 13 can close against its seat 14. Under such conditions, it is difficult for the operator to manually remove the slide 37 from the guide 20 due to the high pressure forcing the slide 37 against the surfaces 33 and 34. In such instance, this high pressure may be released by unscrewing the conical nut 22 a fraction of a turn from the threaded flange 17 so that the adjacent surface of the backup plug 26 is backed away from the tip of the tubular member 15. When this occurs, as shown in FIG. 2, the volume available to contain fluid within the passages 30 and 29 and the space 31 is enlarged and its pressure is quickly reduced to atmospheric. Once the pressure has been reduced, the valve 13 if it has not yet closed, will quickly seat upon its valve seat 14 and prevent further pressure from being applied to the plunger 23. With the plunger 23 no longer under high pressure, the slide 37 can be easily removed from the guide ways 20 and reversed or otherwise repositioned.

The invention above-described thus provides a reversible tip attachment designed for use with conventional airless spray guns which facilitates the removal or reversal of each one of a plurality of restricted orifices, regardless of the liquid operating pressures and regardless of whether an operating orifice becomes completely clogged. It will be apparent that modifications and changes may be made by persons skilled in the art to the abovedescribed preferred embodiment without departing from the spirit and scope of the attached claims.

I claim:

1. A nozzle assembly for a high pressure airless spray gun having a barrel with an axial coating material passage therethrough and a trigger actuated valve controlling said passage, said assembly comprising a body member having a coating material passage and having guiding and retaining ways formed therein transversely to the axis of said coating material passage, means to removably affix said body member to the barrel of said spray gun, a slider member movable in said ways and carrying at least one insert having a restricted orifice therethrough for the discharge of coating material, said slider being completely removable and reversible with respect to said body member, whereby said slider may be removed from said ways, reversed and reinserted into said ways to bring said restricted orifice into re-alignment with said coating material passage in which reversed position the flow of coating material through said orifice is in a reverse direction for cleaning the same.

2. A nozzle assembly in accordance with claim 1 in which said body member has a stepped central bore therethrough, a first coating material directing element in said bore having a passage controlled by said valve, a bored plunger element in said bore axially movable with respect to said body and said first element and having a peripheral hydraulically actuated seal and being adapted to be forced by hydraulic pressure into engagement with said slider whenever said valve is opened to admit coating material to said discharge orifice, the passage in the bore of said plunger element being aligned with the passage forming said discharge orifice in the normal position of said slider.

3. A nozzle assembly in accordance with claim 2, and means to temporarily enlarge the volume of said coating material passages in said body whenever said discharge orifice becomes completely clogged to thereby reduce the fluid pressure tending to urge said slider against its guiding ways.

4. A nozzle assembly in accordance with claim 1 in 5 6 which :said slider member carries a plurality of individ- References Cited ually replaceable spaced inserts each having a restricted UNITED STATES PATENTS discharge orifice therein, which orifices may be selectively brought into juxtaposition with said coating material pas- 442762 12/1890 Wamwnght 239-106 X sage by transverse movement of said slider in said Ways. 5 FOREIGN TENTS 5. A nozzle assembly in accordance with claim 2 in 1,219 1872 Great B i i which said passage controlled by said valve in said first element is displaced from the axis of the bore of said HENSON WOOD Prlmary Emmmg" plunger element, M. Y. MAR, Assistant Examiner. 

